Nyki Blatchley 
Dweller in the Crack [EPUB ebook] 

Kari and Fai, wandering teenage sorcerers and lovers whose spells occasionally work, just want to relax in the city of Jayen-only it’s vanished. Things just get weirder when they learn from a child goddess that the city’s been catapulted thousands of years into the future, and they need to follow it with her to avert disaster.

But the future is more terrifying than they expect-a dystopian technological nightmare, where a crack in reality is keeping two versions of the city trapped. To save Jayen (and maybe the world) Kari and Fai must venture into the Crack and confront the mysterious Dweller within.